CLASS III CRINOIDEA 195 



(?) Bei/rirJiocrinus Waag. and Jahii. Silurian ; Bohemia. 



Gennaeacrinns W. and Sp. Basals three. Calyx low and broad, strongly 

 lobed at the arm bases ; plates thin and highly ornamented. First primibrach 

 hexagonal ; iBr rather numerous. Arm openings twenty-five or more ; arms 

 unknown. Devonian ; Indiana and New York. 



Megistocrinus Owen and Shum. {Tylocrinus Wood). Basals three. Calyx 

 usually large, hemispheric, with greatest height below the arm bases ; usually 

 but little lobed ; plates heavy, smooth or ornamented. Interbrachials 

 numerous ; first primibrach hexagonal. Arms sixteen to twenty, branching 

 in the free state, biserial above and below the bifurcations. Devonian to 

 Lower Carboniferous (Upper Burlington) ; North America. 



Subfamily B. Barrandeocrininae. 



Tegmen narrow and rigid. Arms permanently directed downward enclosing the 



calyx. 



A highly specialised type, represented by a single genus, which, though having a similar 

 calyx, differs so strongly in habitus from those of the next section that it is better kept 

 separate. 



Barrandeocrinus Angelin (Cylicocrinus S. A. Miller). Basals three. Calyx 

 rather elongate, with tegmen nearly flat. Interbrachials few, definitely 

 arranged. Arms ten, heavy, biserial, directed downward over the calyx, with 

 pinnules opening outward. Silurian ; Gotland and North America. 



Subfamily C. Batocrininae. 



Tegmen broad, toell differentiated ; plates large and heavy, forming a rigid roof. 

 Arms not branching beyond the calyx ; biserial. Respiratory pores frequently present. 

 First primibrach (costal) usually quadrangular. Basals three in all known genera. 

 Devonian to Lower Carboniferous. 



This section flourishes amid a remarkable local development of Crinoid life especially 

 characteristic of the Mississippian area of the United States. The founa is enormously prolific 

 in numbers and variety in the Burlington and Keokuk limestones of the Mississippi Valley, but 

 almost entirely wanting in the Lower Carboniferous of Great Britain and Belgium, and of 

 other parts of the United States. Only a few straggling species come from the Devonian. 



§ 1. Anus at the end of a tube. 



a. Interbrachials few, separated from tegmen by arch of brachials. 



Batocrimis Casseday. Calyx biturbinate. Arms short, equidistant. Anal 

 tube very long, central, extending beyond arms. Kinderhook to St. Louis 

 Group ; North America. 



Eretmocrinus Lyon and Cass. Like Batocrimis, but arms paddle-shaped, 

 and anal tube short, eccentric, tending to curve. Devonian to Keokuk 

 Group ; North America. 



Alloprosallocrinus Lyon and Cass. Calyx conical ; dorsal cup almost flat, 

 greatest height above the arm bases. First primibrach usually wanting. 

 Approaching Agaricocrinus in shape. Anal tube sub-central ; arms unknown. 

 Keokuk limestone ; North America. 



p. Interbrachials few, usually separated from the tegmen except at anal side. 



Macrocrinus W. and Sp. Calyx elongate, biturbinate to subovoid. Anal 



